Optical printer

Abstract

In an optical printer apparatus designed so that an optical head ( 100 ) having an LED light source ( 110 ) therein is moved relatively to a sensitized sheet ( 500 ) and an image is formed by emitting a plurality of color light beams in regular order from the LED so that the light beams are focused at given spaces on the sensitized sheet, an image pitch P for the color light beams is substantially equal to an integer multiple of the maximum exposure distance D.

What is claimed is:  
     
       1. An optical printer apparatus which comprises an optical head capable of radiating a plurality of color light beams while moving relatively to a sensitized material, and a drive unit for driving at least one of the optical head and the sensitized material in order to cause the optical head and the sensitized material to move relatively to each other at constant speed, wherein the optical printer apparatus is designed so that individual images formed on the sensitized material when said plurality of color light beams are radiated simultaneously are arranged at given pitches in the direction of said relative movement when the optical head is stationary with respect to the sensitized material, and wherein an image is formed on the sensitized material as the light beams are applied in a predetermined order during said relative movement of the optical head, 
       characterized in that a maximum exposure distance D is smaller than an image pitch P, where the image pitch P is the image pitch of said plurality of color light beams on the sensitized material and the maximum exposure distance D is the relative movement distance of said optical head with respect to said sensitized material, which corresponds to the maximum exposure time of said color light beams.  
     
     
       2. An optical printer apparatus according to  claim 1 , wherein said image pitch P is substantially equal to an integer multiple of said maximum exposure distance D. 
     
     
       3. An optical printer apparatus according to  claim 2 , wherein said plurality of color light beams are applied in a predetermined order in the direction of the movement of said optical head relative to said sensitized material. 
     
     
       4. An optical printer apparatus according to  claim 3 , wherein the relation between the image pitch P and the maximum exposure distance D is given by P=(NC+1)D, where C is the number of color light beams and N is a positive integer not smaller than 1. 
     
     
       5. An optical printer apparatus according to  claim 4 , wherein said number C of color light beams is 3. 
     
     
       6. An optical printer apparatus according to  claim 5 , wherein said color light beams of three different colors include a red light beam, a green light beam, and a blue light beam. 
     
     
       7. An optical printer apparatus according to  claim 6 , wherein said positive integer N is 1, and the relation between the image pitch P and the maximum exposure distance D is given by P=4D. 
     
     
       8. An optical printer apparatus according to  claim 4 , wherein said number C of color light beams is 4. 
     
     
       9. An optical printer apparatus according to  claim 8 , wherein said color light beams of three different colors include a red light beam, a green light beam, and a blue light beam. 
     
     
       10. An optical printer apparatus according to  claim 2 , wherein said plurality of color light beams are applied in an order in the direction opposite to the direction of the movement of said optical head relative to said sensitized material. 
     
     
       11. An optical printer apparatus according to  claim 10 , wherein the relation between the image pitch P and the maximum exposure distance D is given by P=(NC−1)D, where C is the number of color light beams and N is a positive integer not smaller than 1. 
     
     
       12. An optical printer apparatus according to  claim 11 , wherein said number C of color light beams is 3. 
     
     
       13. An optical printer apparatus according to  claim 12 , wherein said color light beams of three different colors include a red light beam, a green light beam, and a blue light beam. 
     
     
       14. An optical printer apparatus according to  claim 13 , wherein said arbitrary position integer N is 1, and the relation between the image pitch P and the maximum exposure distance D is given by P=4D. 
     
     
       15. An optical printer apparatus according to  claim 14 , wherein said number C of color light beams is 4. 
     
     
       16. An optical printer apparatus according to  claim 5 , wherein said color light beams of four different colors include a red light beam, a green light beam, and two blue light beams. 
     
     
       17. An optical printer apparatus according to any one of  claims 1  to  16 , wherein a light source for radiating said color light beams is formed of an LED (light emitting diode). 
     
     
       18. An optical printer apparatus according to any one of  claims 4  to  16 , wherein said optical head carries out gradation control by controlling the exposure time of each pixel in accordance with gradated image data composed of a plurality of pixels, thereby forming a gradated image on said sensitized material. 
     
     
       19. An optical printer apparatus according to  claim 18 , wherein, when any one of said plurality of color light beams undergoes gradation control in accordance with M-th pixel data, as counted in the direction opposite to the moving direction of said optical head with respect to said sensitized material, where M is a positive integer not smaller than 1, and in the case where the color light beam is adjoined by another color light beam in the moving direction of said optical head, said another color light beam undergoes gradation control in accordance with (M+N)-th pixel data based on said positive integer N, as counted in the direction opposite to the moving direction of said optical head, and in the case where the color light beam is adjoined by another color light beam in the direction opposite to the moving direction of said optical head, said another color light beam undergoes gradation control in accordance with (M−N)-th pixel data based on said positive integer N, as counted in the direction opposite to the moving direction of said optical head. 
     
     
       20. A color printing method in which the surface of a sensitized sheet is divided into a plurality of regions (1, 2, 3 . . . N . . . ) in the scanning direction of an optical head and gradations for first, second, and third colors are assigned for each region by image data, comprising steps of: 
       (a) opening a shutter of the optical head, radiating a light beam of a first color with a given width toward an N-th region on the sensitized sheet, then moving the optical head to move the light beam in the scanning direction of the optical head, and closing the shutter in a position reached by the light beam advanced from a radiation start position by a distance d 11  (≦D) assigned by the image data;  
       (b) opening said shutter again after moving the optical head by a distance which allows the light beam of the first color to move for a preset distance D, radiating a light beam of a second color with the width W toward an (N−1)-th region on the sensitized sheet, then moving the optical head to move the light beam in the scanning direction of the optical head, and closing the shutter in a position reached by the light beam advanced from the radiation start position by a distance d 12  (≦D) assigned by the image data;  
       (c) opening said shutter again after moving the optical head by a distance which allows the light beam of the second color to move by the preset distance D, radiating a light beam of a third color with the width W toward an (N−2)-th region on the sensitized sheet, then moving the optical head to move the light beam in the scanning direction of the optical head, and closing the shutter in a position reached by the light beam advanced from the radiation start position by a distance d 13  (≦D) assigned by the image data;  
       (d) opening said shutter again after moving the optical head by a distance which allows the third color light to move by the preset distance D, radiating the light beam of the third color with the width W toward an (N+1)-th region on the sensitized sheet, then moving the optical head to move the light beam in the scanning direction of the optical head, and closing the shutter in a position reached by the light beam advanced from the radiation start position by a distance d 21  (≦D) assigned by the image data; and  
       (e) executing the same operation thereafter.  
     
     
       21. An optical printer apparatus comprising: 
       an optical head radiating a plurality of color light beams while moving relatively to a sensitized material, and  
       a drive unit for driving at least one of the optical head and the sensitized material in order to cause the optical head and the sensitized material to move relatively to each other at constant speed, wherein  
       said color light beams are radiated one by one on a time-sharing basis without simultaneous radiation among them, and in a predetermined order periodically in association with the relative movement of said optical head with respect to said sensitized material, and  
       an image width W of said color light beams on the sensitized material in the direction of said relative movement is smaller than a maximum exposure distance D which is the relative movement distance of said optical head with respect to said sensitized material, and which corresponds to a maximum exposure time of said color light beams.  
     
     
       22. The optical printer apparatus according to  claim 20 , wherein said color light beams are of red (R), green (G), and blue (B) colors.